1. Field of the Invention
The invention relates to the application of a starch and fiber mixture in paper manufacturing. The starch and fiber mixture is applied to a paper mat, after the paper mat is formed. In an embodiment of the invention, the starch and fiber mixture is obtained by the selective filtering of the white water from the papermaking process. The white water is filtered to remove larger particles so that the filtered white water can be used in a spraying process.
2. The Prior Art
Paper and board can be made by a number of processes as known in the art. These processes include the Fourdrinier process, dual former machines, gap former machines and other machines. For example, in the Fourdrinier process, paper and board are generally produced by forming a fiber mat from aqueous cellulosic slurry on a wire screen. These papermaking systems generally comprise a head box having a flow chamber upstream from the wire screen. The head box receives the aqueous cellulosic slurry and deposits the slurry onto the wire screen where a paper mat is formed. The paper mat is removed from the wire screen and further processed, including drying, to form the paper or board.
The aqueous cellulosic slurry generally has a solids content of less than 1% and, therefore, a large amount of liquid is drained off the mat. This liquid is referred to as white water and is a source of fiber. White water comprising fiber is a by-product of most papermaking processes. U.S. Pat. No. 5,942,087 describes the use of fiber from white water that is premixed with granulated starch and then flocculated for use as an additive to paper stock prior to the formation of the paper mat.
We have discovered that a fiber source, including that obtained by white water in a papermaking process, can be sprayed onto the paper mat after its formation to improve the properties of the paper. The fiber source is incorporated into a starch slurry and the resulting starch and fiber mixture is sprayed onto the paper mat. The fiber allows the starch to remain on the mat where it is cooked during further processing. In a preferred embodiment, the white water is selectively filtered, such as in a pressure screen, to obtain optimum sized fiber particles that are capable of being sprayed and will retain the starch on the paper.
In the present Specification, all parts and percentages are on a weight-by-weight basis unless otherwise specified.